With the global reliance on technologies containing fluids for their effective operation it is the case that the quality and technical specification of such fluids be maximised as and when new techniques and materials become available.
There is always an automotive industry requirement for reduced friction for lubricating oils, over broad temperature and torque ranges. Mineral oils are very effective at low temperatures but as the temperature rises their film forming ability diminishes due to a drop in viscosity which impairs the hydrodynamic lubrication regime.
Lubricants also function as a coolant, particularly under high torque conditions. Water is usually the preferred choice for heat removal because of its high thermal conductivity but it is generally unsuitable for use as a lubricant. Gear train lubricants are made primarily from hydrocarbons that have a much lower thermal conductivity and heat capacity than water. Typical gear lubricant base oils include mineral oil, polyalphaolefm, ester synthetic oil, ethylene oxide/propylene oxide synthetic oil, polyalkylene glycol synthetic oil etc. The typical thermal conductivity of these formulations is 0.12 to 0.16 W/m-K at room temperature and they are most effective between 0.12 to 0.14 W/m-K. Water is rated at 0.61 W/m-K.
Synthetic lubricating oils include hydrocarbon oils and halo-substituted hydrocarbon oils such as polymerized and interpolymerized olefins (e.g., polybutylenes, polypropylenes, propylene-isobutylene copolymers, chlorinated polybutylenes, poly(1-octenes), poly(1-decenes), etc., and mixtures thereof; alkylbenzenes (e.g., dodecylbenzenes, tetradecylbenzenes, dinonylbenzenes, di-(2-ethylhexyl)benzenes, etc.); polyphenyls (e.g., biphenyls, terphenyls, alkylated polyphenyls, etc.), alkylated diphenyl, ethers and alkylated diphenyl sulfides and the derivatives, analogs and homologs thereof and the like. Alkylene oxide polymers and interpolymers and derivatives thereof where the terminal hydroxyl groups have been modified by esterification, etherification, etc. constitute another class of known synthetic oils.
Another class of synthetic oils comprises the esters of dicarboxylic acids (e.g., phtalic acid, succinic acid, alkyl succinic acids and alkenyl succinic acids, maleic acid, azelaic acid, suberic acid, sebacic acid, fumaric acid, adipic acid, alkenyl malonic acids, etc.) with a variety of alcohols (e.g., butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol diethylene glycol monoether, propylene glycol, etc.). Specific examples of these esters include dibutyl adipate, di(2-ethylhexyl) sebacate, di-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azealate, dioctyl phthalate, didecyl phthalate, dicicosyl sebacate, the 2-ethylhexyl diester of linoleic acid dimer.
Esters useful as synthetic oils also include those made from C5 to C,2 monocarboxylic acids and polyols and polyol ethers such as neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol, tripentaerythritol, etc. Other synthetic oils include liquid esters of phosphorus-containing acids (e.g., tricresyl phosphate, trioctyl phosphate, diethyl ester of decylphosphonic acid, etc.), polymeric tetrahydrofurans and the like
Polyalphaolefins (PAO) include those sold by Mobil Chemical Company and those sold by Ethyl Corporation however the described invention is not restricted to the products of these companies.
It is in the domain of lubricant improvement that the described invention exists.